// https://www.nowcoder.com/practice/886370fe658f41b498d40fb34ae76ff9

#include <iostream>
#include <vector>
using namespace std;

struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) : val(x), next(nullptr) {}
};

class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param pHead ListNode类
     * @param k int整型
     * @return ListNode类
     */
    ListNode* FindKthToTail(ListNode* pHead, int k) {
        ListNode* fast = pHead;
        ListNode* slow = pHead;
        int i = 0;
        for (; i < k && fast != nullptr; i++) {
            fast = fast->next;
        }
        if (fast == nullptr) {
            if (i < k) {
                return nullptr;
            }
            return pHead;
        }
        while (fast != nullptr) {
            slow = slow->next;
            fast = fast->next;
        }

        return slow;
    }
};